1. Field of the Invention
The present invention relates to a digital television system, particularly to a PID/section filter which is adapted without any restriction to an ATSC (Advanced Television System Committee) standard for a digital television broadcasting in U.S.A or a DVB (Digital Video Broadcasting) standard for a digital satellite broadcasting in Europe.
2. Description of the Related Art
In a digital television system using a MPEG2 standard such as ATSC (Advanced Television System Committee) standard for a digital television broadcasting in U.S. or a DVB (Digital Video Broadcasting) standard for a digital satellite broadcasting in Europe, a transport stream is a means of multiplexing an audio/video stream of various programs by packet using an error correction code and transmitting the multiplexed audio/video stream.
The transport stream is transmitted by a predetermined transmission unit (example; 188 byte), the each unit of transport stream includes a PID (Packet Identifier) as information showing what information is contained in the corresponding transport stream. Accordingly, the PID/section filter in receiving part decodes transport stream being received, extracts the information requested by a viewer from the decoded information, and downloads it to an external device, stores it in a memory, or discards it on the basis of the PID.
However, general PID/section filters have a structure that can support either ATSC standard or DVB standard.
As an example of the general PID/section filters, a SGS-Thomson""s ST20-TP2 chip decodes a DVB stream by using a processor, and a section filtering part is constructed as a hardware. And the chip includes thirty two filters for filtering thirty two sections of the packet at the same time, wherein each filter requires 8 byte section header data and 8 byte mask data for designating whether the 8 byte section header data is used for filtering or not. Accordingly, a fixed memory of the total 512 byte (32xc3x978xc3x972=512) is used. However, there is a limitation to perform filtering by using the SGS-Thomson""s ST20-TP2 chip because in both ATSC and DVB systems there are sections including some fields additionally required for filtering besides the basic 8 byte.
As another example of the general PID/section filters, a PID/section filter of a LG""s GDC21S802A chip specialized for the ATSC has a disadvantage that it can not support the DVB or other standard.
As further example of the general PID/section filters, LSI Logic L64118 chip with combined function of ATSC and DVB systems comprises thirty two PID registers, and supports section filtering for thirty PIDs. The LSI Logic L64118 comprises thirty two filters, each filter is constructed as data for filtering up to 12 byte including a section header. However, such a decoding chip has a disadvantage of low efficiency in the memory.
As described above, since the PID/section filters according to the conventional technology can support only one of the ATSC standard or the DVB standard, an application range of a product is limited, filtering is limited due to the limitation of the field used as the section filter, and resources are squandered away since the memory is inefficiently used.
The object of the present invention is to provide a PID/section filter which is capable of supporting both an ATSC standard and a DVB standard, and maximizing the efficiency of a memory.
In order to achieve the object, the PID/section filter according to the present invention comprises: a processor module for decoding an input transport stream, detecting a PID(Packet ID) and a TID(Table ID) from the decoded transport stream, and extracting a viewer requested information from the decoded information; a PID comparing circuit module for comparing a PID value received from the processor module with a PID value stored in each internal register and feeding back the comparing result to the processor module; a download circuit module for downloading the information extracted from the information decoded by the processor module to an external device upon request of the viewer; and an external memory module for storing the information extracted upon request of the viewer in an external memory.
The PID/section filter according to the present invention further comprises an external controller module for recording the PID value corresponding to the viewer requested information on the PID comparing circuit module, and recording the information to be filtered by the processor module in a filter memory.